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DP83867ERGZ-S-EVM: hardware setup questions

Michael T Schneider
Expert 3790 points
Part Number: DP83867ERGZ-S-EVM

Hello Team, 

I have a design using the DP83867ERGZ and have a few questions - searching through other e2e posts I believe I found answers to a few questions but wanted to check with you all first. 

  1. Which power is for the PHY to transformers – VDDIO, VDDA2P5, or VDDA1V0? Is it VDDIO?
  2. Datasheet and Eval board Users guide are inconsistent with decoupling caps – datasheet says10 nF cap, eval board shows 1nF cap. Which one is correct?
  3. In 10Base-T/100Base_Tx, what do I do with TD_A_P/N, and TD_B_+/N? TD_C_P/N and TD_D_P/N are connected to transformers (TX+/-, Rx+/-).
    1. No unused pins have special termination requirements
  4. Figure 20 in datasheet says: I need to strap resistors for RX_D[0:3]. But, I didn’t see that in the eval board user’s guide. What should I do?
    1. Strap pins have internal 9k ohm pull-down resistors. It is not required to add external pulls, but some people still do it for good practice.
  5. If I use only the SGMII interface (that is, SGMII_SI[P/N], SGMII_SO[P/N]), what do I do with the rest MAC interface pins?

Thank you!

  • 0
    TI__Mastermind 18425 points
    Hi Michael,

    Thanks for reaching out with your questions. We will get back to you by 08/28.

    -Regards,
    Aniruddha
  • 0 in reply to Aniruddha Khadye
    TI__Expert 3790 points

    Thank you Aniruddha, 

    I will look out for your response.

    Best Regards-

  • 0 in reply to Michael T Schneider
    TI__Mastermind 18425 points
    Hi Micheal,

    DP83867 PMD does not need to be pulled up to any voltage rail, so there would be not power supply connected to the magnetics. Magnetics center tap should be connected to ground via decoupling caps. Magnetics center taps should not be tied to each other.

    Please follow the datasheet recommendation for supply decoupling caps.

    During 100Mbps more and 10Mbps mode, the unused PMD channels will be inactive. There is no need for separate termination strategy. Note that the EVM has Mirror Mode enable which is the reason why the PMD channels are routed in the way that they are. If you plan to use the connections as shown on the EVM, ensure that mirror mode is on via strap or register configuration.

    Your comment is correct. The internal strap resistors are weak and its generally a good idea to provision for external pull resistors in order to prevent any other resistances from disturbing the strapping scheme. Please note that RX_CTRL needs to be strapped to mode 3 for auto-negotiation on.

    If only SGMII is required then other MAC pins can be left floating. Note that RGMII RX pins are strap pins and they will continue to behave as strap pins even in RGMII mode. The above comment about RX_CTRL will be applicable even in SGMII mode.

    -Regards,
    Aniruddha